AussieSteve
Active Member
Best generators for purpose.
Checked eBay yet?
Before you do - If you really want 100W at 12VDC, look for a 24V DC brush-motor with a power rating of about double that, ie 200W. Fairly large though.
Also, ensure that you pick a motor with a usable RPM. My first attempt was with a motor that I discovered was built to run at 18000rpm at 12V, no good at all. (Didn't really know how fast it spun until I bought an optical tacho for testing. Turns out that at one point I was spinning it at 23,000rpm. Wonder how long it would have lasted?))
Also, maximum efficiency is obtained when drawing 50% of the motor's short-circuit current, which is at about half of it's open-circuit voltage.
A 24V motor will generate 24V at it's rated RPM, open-circuit.
Under load, that voltage drops. At max efficiency in the example above, the output voltage would be 12V at half the S.C. current.
Finally, check out DC electric scooter motors. Splashproof, low RPM, ball-bearings for continuous use and fairly cheap for the quality.
I'm using a 24V 100W 2500RPM 'Razor' scooter DC brush-motor, belt-driven from my shift-kit's jackshaft, into a (DIY) regulator and 12V 5Ah battery. (Not completed.)
Checked eBay yet?
Before you do - If you really want 100W at 12VDC, look for a 24V DC brush-motor with a power rating of about double that, ie 200W. Fairly large though.
Also, ensure that you pick a motor with a usable RPM. My first attempt was with a motor that I discovered was built to run at 18000rpm at 12V, no good at all. (Didn't really know how fast it spun until I bought an optical tacho for testing. Turns out that at one point I was spinning it at 23,000rpm. Wonder how long it would have lasted?))
Also, maximum efficiency is obtained when drawing 50% of the motor's short-circuit current, which is at about half of it's open-circuit voltage.
A 24V motor will generate 24V at it's rated RPM, open-circuit.
Under load, that voltage drops. At max efficiency in the example above, the output voltage would be 12V at half the S.C. current.
Finally, check out DC electric scooter motors. Splashproof, low RPM, ball-bearings for continuous use and fairly cheap for the quality.
I'm using a 24V 100W 2500RPM 'Razor' scooter DC brush-motor, belt-driven from my shift-kit's jackshaft, into a (DIY) regulator and 12V 5Ah battery. (Not completed.)
Last edited:
